Memory devices are typically provided as internal, semiconductor, integrated circuits in computers or other electronic devices. There are many different types of memory including volatile and non-volatile memory. Volatile memory can require power to maintain its data (e.g., host data, error data, etc.) and includes random-access memory (RAM), dynamic random access memory (DRAM), and synchronous dynamic random access memory (SDRAM), among others. Non-volatile memory can provide persistent data by retaining stored data when not powered and can include NAND flash memory, NOR flash memory, read only memory (ROM), Electrically Erasable Programmable ROM (EEPROM), Erasable Programmable ROM (EPROM), and resistance variable memory such as phase change random access memory (PCRAM), resistive random access memory (RRAM), and magnetoresistive random access memory (MRAM), among others.
Memory devices can be combined together to form a storage volume of a memory system such as a solid state drive (SSD). A solid state drive can include non-volatile memory (e.g., NAND flash memory and NOR flash memory), and/or can include volatile memory (e.g., DRAM and SRAM), among various other types of non-volatile and volatile memory. Memory is used herein to refer to a group of memory cells, which may be arranged as a memory array, a memory device, a memory system, or other one of various configurations.
An SSD can be used to replace hard disk drives as the main storage volume for a computer, as the solid state drive can have advantages over hard drives in terms of performance, size, weight, ruggedness, operating temperature range, and power consumption. For example, SSDs can have superior performance when compared to magnetic disk drives due to their lack of moving parts, which may avoid seek time, latency, and other electro-mechanical delays associated with magnetic disk drives.
Upon power loss while writing data to a memory device, memory cells can be left in an uncertain condition. Memory can have memory cells that are partially (e.g., shallowly) programmed but appears to be erased. Memory can have memory cells that are incompletely programmed to within a target threshold voltage range of an intended data state but perhaps only barely within so as to marginally pass a verification read. Memory can have memory cells that are insufficiently programmed with respect to the target threshold voltage range of the intended data state, which can result in Error Correction Code (ECC) errors. Condition of memory cells in progress of being programmed when a power loss occurs can vary depending on the data state being programmed, location of the memory cell with respect to an upper page, lower page, even page, odd page, and number of data states to which the memory cell is being programmed, among others. Upon power-up, the various conditions of the memory cells of the memory can affect data integrity of the memory device and performance of the host computing system in different ways.
Detection of a number of ECC errors associated with a memory can result in the host computing system identifying a portion of the memory (e.g., page) as being corrupted, which can cause the host computing system to waste time and energy attempting to correct the ECC errors and/or unnecessarily stop using the portion of the memory. Memory that has memory cells that are shallowly programmed (e.g., not fully erased) but appear to be erased can be sensitive to Program Disturb if the host computing system attempts to program new data to the memory cells on top of the shallowly programmed condition of the memory cells. Memory cells that are incompletely programmed within a threshold voltage range but pass a verification read can be more susceptible to data retention issues under certain conditions such as at higher temperatures.
Power loss while erasing data from a memory (e.g., programming a memory cell to an erase state) can result in partially erased pages that are susceptible to Disturb and misplacement. Accordingly, apparatus and methods to assess and address memory cell conditions following a power loss can improve operation of a memory device.